Development of Nb–NiMoO4/g-C3N4 direct Z scheme heterojunctions for effective photocatalytic conversion of carbon dioxide to valuable products

Herein, Nb was successfully doped into the NiMoO4 lattice. These Nb dopants existing in the NiMoO4 lattice effectively enhanced visible light absorbance and decreased band-gap energy of the material from 2.45 to 2.23 eV. The Nb doped NiMoO4 (Nb–NiMoO4) was also successfully hybridized with g-C3N4 to form direct Z heterojunction (Nb–NiMoO4/g-C3N4) for novel photocatalytic performance. The photo-current response under visible light of the synthesized Nb–NiMoO4/g-C3N4 was approximately (∼52.11 μA/cm2), which was the highest among the photo-current responses of these synthesized materials. The produced electrons of the Nb–NiMoO4/g-C3N4 existed at the conduction band of the g-C3N4 while the produced holes existed in the valence band of the Nb–NiMoO4. Thus, the generated charges had high redox potential for effective conversion of carbon dioxide to CH4, HCOOH, CO and O2. Production rates of CH4, HCOOH, CO and O2 from CO2 conversion by Nb–NiMoO4/g-C3N4 heterojunction were 769, 587, 356 and 1960 (μmol. g−1cat. h−1). Finally, the formed Nb–NiMoO4/g-C3N4 heterojunction also presented novel stability during long period CO2 conversion. The obtained results could be utilized for valuable fuel production in practical systems.